There are disclosed a distance measuring equipment capable of performing a distance measurement with greater accuracy suppressing cost up, and a camera. In case of the short distance area and the middle distance area, switches 61 and 62 are set up to the turn-off state, and switch 63 is set up to take the contact 63a side, so that photo-current signals I1 and I2 from PSD 30 are fed to input terminals 41 and 42 to perform a usual ratio arithmetic processing. In case of the long distance area, the switches 61 and 62 are set up to the turn-off state and the turn-on state, respectively, and the switch 63 is set up to take the contact 63b side, so that photo-current signal the I1 and fixed current signal Ir are fed to the input terminals 41 and 42 to perform a ratio arithmetic processing based on the fixed current signal. In case of the longest distance area, the switches 61 and 62 are set up to the turn-on state and the turn-off state, respectively, and the switch 63 is set up to take the contact 63b side to form a first signal transmission path, so that an addition value of the photo-current signals I1 and I2 and the fixed current signal Ir are fed to the input terminals 41 and 42 to perform a ratio arithmetic processing based on light quantity to determine focusing data.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A distance measuring equipment for measuring a distance up to a target to be measured in distance in such a manner that light is projected and light reflected on the target and returned is detected, said distance measuring equipment comprising: a semiconductor photo detector element having a detection surface generating a photo-current upon receipt of irradiation of light; a ratio arithmetic circuit, having two input terminals each for receiving associated one of current signals, for performing a ratio arithmetic operation in accordance with the current signals fed from the two input terminals; a current source for generating fixed current signal; and a first signal transmission path wherein the photo-current obtained through irradiation of light onto the detection surface of said semiconductor photo detector is lead to one input terminal of the two input terminals of said ratio arithmetic circuit and the fixed current signal from said current source to another input terminal of the two input terminals of said ratio arithmetic circuit.
2. A distance measuring equipment according to claim 1 , wherein said current source generates a fixed current signal.
3. A distance measuring equipment according to claim 1 , wherein said semiconductor photo detector element comprises a plurality of signal electrodes for outputting on a shared basis the photo-current generated on said detection surface, and said first signal transmission path leads photo-currents outputted on a shared basis from said plurality of signal electrodes to said one input terminal.
4. A distance measuring equipment according to claim 3 , wherein said semiconductor photo detector element comprises said detection surface, and a pair of signal electrodes, disposed at both ends of said detection surface, adapted for outputting on a shared basis the photo-current generated by irradiation of light onto said detection surface in accordance with respective distances between an irradiation position on said detection surface and both ends of said detection surface.
5. A distance measuring equipment according to claim 1 , wherein said semiconductor photo detector element comprises said detection surface, a pair of signal electrodes, disposed at both ends of said detection surface, adapted for outputting on a shared basis the photo-current generated by irradiation of light onto said detection surface, and a first switch, disposed at a position adjacent to one signal electrode which is one of said pair of signal electrodes, for selectively offering a first state which permits the photo-current generated on said detection surface to conduct into said one signal electrode, and a second state which inhibits the photo-current generated on said detection surface from conducting into said one signal electrode, in accordance with a control signal, and said first signal transmission path leads, when said first switch offers said second state, the photo-current outputted from another signal electrode different from said one signal electrode of said pair of signal electrodes to said one input terminal.
6. A distance measuring equipment according to claim 5 , wherein in said semiconductor photo detector element, when said first switch is in the first state, said pair of signal electrodes output on a shared basis the photo-currents generated by irradiation of light onto said detection surface in accordance with respective distances between an irradiation position of the light on said detection surface and both the ends of the detection surface.
7. A distance measuring equipment according to claim 5 , wherein said first state is a low impedance state, and said second state is a high impedance state.
8. A distance measuring equipment according to claim 1 , wherein said semiconductor photo detector element comprises said detection surface, said detection surface being divided into first and second divided areas, first and second signal electrodes, said first signal electrode connected to the first divided area of said detection surface, and said second signal electrode connected to the second divided area of said detection surface, said first and second signal electrodes adapted for outputting the photo-current generated by irradiation of light onto said detection surface, and a second switch, disposed at a boundary between divided areas of said detection surface, for selectively offering a first state which permits the photo-current generated on said detection surface to conduct through the associated boundary, and a second state which inhibits the photo-current generated on said detection surface from conducting through the associated boundary, in accordance with a control signal, and said first signal transmission path leads, when said second switch offers said first state, the photo-current outputted from the first and second signal electrodes on a shared basis to said one input terminal.
9. A distance measuring equipment according to claim 8 , wherein said first state is a low impedance state, and said second state is a high impedance state.
10. A distance measuring equipment according to claim 1 , wherein said semiconductor photo detector element comprises said detection surface, said detection surface being divided into first and second divided areas, first and second signal electrodes, said first signal electrode connected to the first divided area of said detection surface and said second signal electrode connected to the second divided area of said detection surface, said first and second electrodes being adapted for outputting the photo-current generated by irradiation of light onto said detection surface, a second switch, disposed at a boundary between divided areas of said detection surface, for selectively offering a first state which permits the photo-current generated on said detection surface to conduct through the associated boundary, and a second state which inhibits the photo-current generated on said detection surface from conducting through the associated boundary, in accordance with a control signal, and a third switch, provided in association with another signal electrode excepting a first signal electrode which is one of said signal electrodes, for selectively offering a first state which permits the photo-current generated on said detection surface to conduct into the associated signal electrode, and a second state which inhibits the photo-current generated on said detection surface from conducting into the associated signal electrode, in accordance with a control signal, and said first signal transmission path leads, when said third switch offers said second state, while said second switch offers said first state, the photo-current outputted from the first signal electrode to said one input terminal.
11. A distance measuring equipment according to claim 8 , wherein said first state is a low impedance state, and said second state is a high impedance state.
12. A distance measuring equipment according to claim 1 , wherein said semiconductor photo-detector element has a plurality of signal electrodes adapted for outputting on a shared basis the photo-current generated on said detection surface, and distance measuring equipment further comprises a transmission path selecting unit for changing over between said first signal transmission path and a second signal transmission path for leading two types of photo-currents outputted from two signal electrodes of the plurality of signal electrodes of said semiconductor photo detector element to the two input terminals of said ratio arithmetic circuit, respectively.
13. A distance measuring equipment according to claim 1 , wherein said semiconductor photo detector element has a plurality of signal electrodes adapted for outputting on a shared basis the photo-current generated on said detection surface, and distance measuring equipment further comprises a transmission path selecting unit for changing over between said first signal transmission path and a second signal transmission path for leading one photo-current of a plurality of photo-currents outputted from the plurality of signal electrodes of said semiconductor photo detector element to one of the two input terminals of said ratio arithmetic circuit, and for leading a fixed current signal from said current source to another input terminal of the two input terminals of said ratio arithmetic circuit.
14. A distance measuring equipment according to claim 1 , wherein said semiconductor photo detector element has a plurality of signal electrodes adapted for putting on a shared basis the photo-current generated on said detection surface, and distance measuring equipment further comprises a transmission path selecting unit for changing over between said first signal transmission path, a second signal transmission path for leading two types of photo-currents outputted from two signal electrodes of the plurality of signal electrodes of said semiconductor photo detector element to the two input terminals of said ratio arithmetic circuit, respectively, and a third signal transmission path for leading one photo-current of a plurality of photo-currents outputted from the plurality of signal electrodes of said semiconductor photo detector element to one of the two input terminals of said ratio arithmetic circuit, and for leading a fixed current signal from said current source to another input terminal of the two input terminals of said ratio arithmetic circuit.
15. A camera having a distance measuring equipment for projecting light for focusing in front of the camera and detecting light reflected on a subject to determine a distance up to the subject, said distance measuring equipment moving an image taking lens to the determined distance for photography, wherein said distance measuring equipment comprises: a semiconductor photo detector element having a detection surface generating a photo-current upon receipt of irradiation of light; a ratio arithemetic circuit, having two input terminals each for receiving associated one of current signals, for performing a ratio arithmetic operation in accordance with the current signals fed from the two input terminals; a current source for generating fixed current signal; and a first signal transmission path wherein the photo-current through irradation of light onto the detection surface of said semiconductor photo detector is lead to one input terminal of the two input terminals of said ratio arithmetic circuit and the fixed current signal from said current source to another input terminal of the two input terminals of said ratio arithmetic circuit.
16. A camera according to claim 15 , wherein said semiconductor photo detector element has a plurality of signal electrodes adapted for outputting on a shared basis the photo-current generated on said detection surface, and distance measuring equipment further comprises a transmission path selecting unit for changing over between said first signal transmission path and a second signal transmission path for leading two types of photo-currents outputted from two signal electrodes of the plurality of signal electrodes of said semiconductor photo detector element to the two input terminals of said ratio arithmetic circuit, respectively.
17. A camera according to claim 15 , wherein said semiconductor photo detector element has a plurality of signal electrodes adapted for outputting on a shared basis the photo-current generated on said detection surface, and distance measuring equipment further comprises a transmission path selecting unit for changing over between said first signal transmission path and a second signal transmission path for leading one photo-current of a plurality of photo-currents outputted from the plurality of signal electrodes of said semiconductor photo detector element to one of the two input terminals of said ratio arithmetic circuit, and for leading a fixed current signal from said current source to another input terminal of the two input terminals of said ratio arithmetic circuit.
18. A camera according to claim 15 , wherein said semiconductor photo detector element has a plurality of signal electrodes adapted for outputting on a shared basis the photo-current generated on said detection surface, and distance measuring equipment further comprises a transmission path selecting unit for changing over between said first signal transmission path, a second signal transmission path for leading two types of photo-currents outputted from two signal electrodes of the plurality of signal electrodes of said semiconductor photo detector element to the two input terminals of said ratio arithmetic circuit, respectively, and a third signal transmission path for leading one photo-current of a plurality of photo-currents outputted from the plurality of signal electrodes of said semiconductor photo detector element to one of the two input terminals of said ratio arithmetic circuit, and for leading a fixed current signal from said current source to another input terminal of the two input terminals of said ratio arithmetic circuit.
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July 27, 2000
February 5, 2002
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